A Unified Phenomenology of Ion Heating in Low-$\beta$ Plasmas: Test-Particle Simulations

Abstract

We argue that stochastic and resonant ion heating, often viewed as distinct processes in low-$\beta$ collisionless plasmas, are the far limits of a continuum controlled by nonlinear broadening of turbulent fluctuations, and thus by the normalized cross helicity. We propose a simple empirical formula that captures both regimes, generalizing that commonly used to describe stochastic heating. Simulations of test ions interacting with turbulence confirm our scalings across a wide range of different ion and turbulence properties, including with a steep ion-kinetic transition range as seen in the solar wind. Our results provide a unified framework for understanding ion heating processes across diverse astrophysical environments from black-hole accretion disks to the solar corona, also providing a compact and versatile subgrid model for larger-scale simulations.

Accepted for publication in Physical Review Letters. 14 pages, 5 figures; includes supplemental material (6 figures)

References in corpus (16)

• Imbalanced Strong MHD Turbulence
• Strong Imbalanced Turbulence
• Collisionless Reconnection in Magnetohydrodynamic and Kinetic Turbulence
• Hybrid-Kinetic Simulations of Ion Heating in Alfvénic Turbulence
• Violation of the zeroth law of turbulence in space plasmas
• The In Situ Signature of Cyclotron Resonant Heating
• Inner-Heliosphere Signatures of Ion-Scale Dissipation and Nonlinear Interaction
• Nature of stochastic ion heating in the solar wind: testing the dependence on plasma beta and turbulence amplitude
• On stochastic heating and its phase-space signatures in low-$\beta$ kinetic turbulence
• The Enhancement of Proton Stochastic Heating in the near-Sun Solar Wind
• Adaptive critical balance and firehose instability in an expanding, turbulent, collisionless plasma
• Radial evolution of stochastic heating in low-$\beta$ solar wind
• Evidence for the helicity barrier from measurements of the turbulence transition range in the solar wind
• Electron-ion heating partition in imbalanced solar-wind turbulence
• Acceleration of Particles in Imbalanced Magnetohydrodynamic Turbulence
• The effects of finite electron inertia on helicity-barrier-mediated turbulence

Cited by in corpus (3)

• Chaotic Motion of Ions In Finite-amplitude Low-frequency Alfvén Waves
• Perpendicular ion heating in turbulence and reconnection: magnetic moment breaking by coherent fluctuations
• Turbulent heating in collisionless low-beta plasmas: imbalance, Landau damping, and electron-ion energy partition